In take-off of a conventional aircraft, the aircraft accelerates along a runway until it reaches take-off speed. Then, by operation of control surfaces (usually elevators) the angle of attack of the principal airfoil surface (usually the wings) is increased in order to increase lift to a value exceeding the aircraft's weight. The attitude typically is maintained during climb, whereupon the angle of attack is typically decreased for level flight at a cruising altitude.
In landing, with the engine throttled back so that the aircraft descends as it approaches the runway, the angle of attack is increased slightly to increase lift so that the aircraft can touch down gently and brake to a stop.
In both cases, the angle of attack of the aircraft is carefully limited in order to avoid stall, which would result in loss of control, and generally, the aircraft is controlled so that the lift coefficient is limited to a fraction of the maximum lift coefficient, based on the lift curve which characterizes the airfoil surface in steady flow, taking into account trim, flap settings, etc. Typically, the lift coefficient is limited to about 80% of the maximum lift coefficient.
In conventional take-off and landing, the ground roll during take-off is relatively long, the ground roll following touchdown is also relatively long. These long ground roll distances require long runways, and have led to the development of various techniques for short take-off and landing (STOL), including high lift devices, rocket boosters, tilting engines, etc.
An object of this invention is to achieve short take off and landing performance in an aircraft without the need for expensive attachments and modifications. The invention takes advantage of a phenomenon known as “dynamic lift overshoot,” in which, as the angle of attack of an airfoil is continuously increased, the lift coefficient CL can, for a short time, exceed CLmax, the peak value of the lift curve for the airfoil under steady flow conditions. Dynamic lift overshoot can be predicted and controlled in such a way as to produce increased lift while avoiding stall and departure. Thus, controlled use of dynamic lift overshoot can significantly reduce take-off and landing speeds, and shorten runway length requirements.